The major objective of this research proposal is to investigate the mechanisms of insulin resistance (IR) seen in association with acanthosis nigricans (AN) and/or hirsutism (H). Human skin fibroblasts (F) obtained from forearm biopsy of nine individuals who have been indentified as having severe IR with AN and H will be utilized to determine if instrinsic defects in insulin action (IA) are present which result in the IR seen in the type A syndrome of IR and AN. In vitro studies will involve mearurements of insulin binding, association:dissociation studies, insulin internalization and intracellular degradation, insulin mediated receptor regulation, insulin receptor regeneration following down-regulation, and insulin stimulation of 2-deoxyglucose uptake and glucose oxidation. In addition, to determine if hyperandrogenemia directly affects IA, thus contributing to the IR seen in this syndrome, the ability of androgens (A) to directly alter IA at the receptor and/or post-receptor level will be assessed in vitro utilizing normal and subject F. Effects of acute and chronic A exposure on insulin binding, insulin internalization and degradation, receptor regulation and glucose metabolism will be directly assessed. Lastly, insulin and somatomedin-C binding will be evaluated in F obtained from skin sites involved with AN and the results compared with cells obtained from non-involved sites in the same individual to determine if differences in receptor populations are present which might contribute, via an insulin mediated mitotic mechanism, to the hyperplastic epidermal response seen in the acanthotic regions. It is expected that these studies will answer key questions regarding the IR seen in this syndrome. In addition, the studies involving the direct effects of A on IA should add significantly to our understanding of the interaction of sex hormones and carbohydrate tolerance. Further, the studies involving cells obtained from skin sites involved with AN have the potential to shed important light on the association of IR and AN. Most importantly, the identification an evaluation of human cells with specific intrinsic insulin receptor/post receptor defects will provide a potent model for future investigation of IA which will be applicable to more common pathophysiologic states such as diabetes mellitus. Thus, a clearer understanding of mechanisms of IR in various human disease states should lead to newer and more rational therapeutic approaches.